Wearable devices are becoming increasingly popular. For example, wearable devices equipped with sensors are known that may track user data such as activity data (duration, step count, calories burned), sleep statistics, and/or physiological data (e.g., heart rate, perspiration and skin temperature). Typically, sensor-equipped wearable devices are implemented as bands or watches that may be worn on the user's wrist. However, conventional wearable sensor devices require the user discard or replace the entire device due to a loss of function, even if the loss is caused by a relatively minor component, such as a sensor that becomes worn out due to normal wear. Users also often replace the device when a new device with new or different tracking functions becomes available.
Accordingly, what is needed is an improved architecture for wearable sensor devices that can accommodate both replacement and addition of sensor functionality.